1. Field of the Invention
The invention relates to the field of maintenance docks for aircraft and similar large elongated vehicles.
2. Background Art
To be able to carry out maintenance and painting work on aircraft, maintenance docks are used which include working floors carried by a frame, from which floor workers have access to the exterior of the aircraft. To carry out work, these maintenance docks are typically erected in such a way as to be adjacent to the outer skin of the aircraft. The docks have in each case openings through which the wings of the aircraft pass. To be able to dock and undock the aircraft without dismantling the dock it has already been proposed to arrange the frame of the dock so as to be displaceable in a lateral direction on the floor of the maintenance hangar (EP 0 568 543 A1).
This manner of enabling docking and undocking presupposes, however, that the hangar is large enough to allow a correspondingly large lateral displacement of the dock. The hangar must, therefore, be wider than the wingspan of the largest aircraft to be serviced by at least twice the transverse dimension of the dock units erected on each side of the fuselage. For practical embodiments of dock units, this dimension is approx. 10 m. For the time needed for docking and undockingxe2x80x94which is short in comparison to the time for the work at the dock (a few days for minor maintenance and a few months for the D check)xe2x80x94the maintenance hangar must, therefore, be built significantly larger than is necessary for its actual purpose.
A larger maintenance hangar means not only higher construction costs but also higher continuous operating costs. For example, in hangars in which aircraft are painted an unnecessarily large volume of air must be maintained at drying temperature over relatively long periods. In addition, to ensure the laminar airflow used for drying freshly painted aircraft greater expenditure is needed in larger hangars.
The heating costs and the costs for maintaining clean air and air disposal are also increased.
In addition, in the case of some existing hangars it would be desirable to be able to service aircraft with still larger wingspans without reconstruction of the hangar.
It is, therefore, the object of the invention to specify a maintenance dock for aircraft in which docking and undocking is possible without transverse displacement of the dock units beyond the wingtips.
This object is achieved according to the invention by a maintenance dock having a frame (22) which carries at least one working floor and is supported in an unchangeable manner at one end (18) and an outer end of which rests on a floor (36) via an outer support (42), characterized in that the frame (22) is supported on the floor (36) via at least one further, inner support (44) and the outer support (42) and the further, inner supports (44) are movable between a prop position in which they engage supportingly against the frame (22) and a clearance position in which they open a passage (38) between the frame (22) and the floor (36).
Common to the various embodiments of the invention is the idea of removing for a short time a support supporting the frame of a dock unit on the erection surface and thereby producing in the area of this support a temporary passage for the wing of an aircraft. In this time, the frame is supported on the erection surface by a different measure, which according to one embodiment is a further, inner support and according to another embodiment is a suspension arrangement.
Because the time for docking and undocking is short and because, in order to dock and undock the aircraft, any especially heavy equipment and local material stores located in the dock unit can be removed, the further, inner support or suspension arrangement need not be designed especially strong or engage at precisely the same point on the frame as the outer support which normally supports a front section of the frame.
According to the invention, therefore, a passage for the aircraft wing is created for a short time for docking and undocking. The dock unit thus in a sense climbs over the wing of the moving aircraft. Where a dock unit rests on the erection surface via a multiplicity of supports the appropriate supports, in so far as they are located in the path of the wings of the aircraft to be maintained, can all be made movable, a passage which moves along with the aircraft wing being created between the underside of the dock frame and the erection surface by pulling up a support or a group of supports in each case. It is self-evident that, in the case of a multiplicity of such supports, the change in the loading of the dock frame caused by moving one of the supports from the prop position supporting the frame to a clearance position creating said passage is proportionally smaller.
The solution according to the invention can be used equally for docking an aircraft in the forward direction (nose in) and in the reverse direction (tail in).
Because the maintenance dock according to the invention can remain standing during docking and undocking, all the line connections between the dock unit and the hangar can also remain unchanged (electric leads, fluid lines, ventilation shafts and so on). This simplifies and shortens the process of docking and undocking.
Because no dead spaces which serve only to accommodate the dock unit during docking and undocking have to be provided in the maintenance hangar when using the dock unit according to the invention, considerable savings can be made in the construction, maintenance and operating costs of the maintenance hangar. Aircraft whose wingspans are only slightly shorter than the clear width of the hangar itself can be maintained in existing maintenance hangars.
In the claims and in the present description, directional indications relating to the maintenance hangar and to the direction of movement of the aircraft during docking and undocking are used. Maintenance hangars have large doors through which the aircraft are towed into and out of the hangar. Where these doors are located is xe2x80x9coutsidexe2x80x9d. An opposite wall of the maintenance hangar in which storage rooms, workshops and offices are usually arranged is located xe2x80x9cinsidexe2x80x9d. The direction perpendicular (from xe2x80x9coutsidexe2x80x9d to xe2x80x9cinsidexe2x80x9d) to the wall containing the door is the direction in which a dock unit placed beside the aircraft extends. This direction corresponds to the longitudinal axis of the aircraft. xe2x80x9cAbovexe2x80x9d and xe2x80x9cbelowxe2x80x9d correspond to normal linguistic usage.
For each of the dock units, xe2x80x9cinwardxe2x80x9d means the side facing towards the aircraft while xe2x80x9coutwardxe2x80x9d means the side facing away from the aircraft.
Transverse means perpendicular to the longitudinal direction of the dock or to the longitudinal axis of the aircraft.
Advantageous refinements of the invention are specified in the subsidiary claims.
Having supports which are adjustable in the vertical direction is especially advantageous with regard to space utilization. The displaceable supports occupy the same space in both working positions when seen from above.
In one embodiment of the invention, the vertically adjustable support is attached to the frame. Such a refinement of the invention has the advantage that no constructional alterations to the hangar are necessary. A dock unit according of such an embodiment can be installed without difficulty in existing maintenance hangars.
In one embodiment, at least one of the supports is retractable into the floor. Such a refinement of the invention has the advantage that the dock frame does not need to carry the adjustable supports and the drives acting on them.
In one such embodiment, the free end face of the supports which are retractable into the floor are flush with the floor in the fully retracted state. In such a case, a continuous flat floor area of the maintenance hangar can be ensured by complete retraction of the vertically movable supports into the erection surface.
In another embodiment of the invention, at least one of the supports is movable across the floor. Such a refinement of the invention has the advantage that neither constructional measures relating to the building nor special measures relating to the dock frame need to be provided. The latter need neither support the weight of the displaceable supports in their clearance position nor carry drives for moving the displaceable supports.
In one such embodiment of the invention, the at least one support which is movable across the floor can be coupled to a vehicle or carriage which runs on the floor. Such a refinement is advantageous in that displacement of the movable supports can be effected simply and quickly.
In one such embodiment, at least one of the supports which are movable across the floor is of lower height than the passage between the underside of the frame and the floor and has an adjustable strut, the stroke of which is short in comparison to the height of the passage. The total height of the support and the adjustable strut in the fully extended state of the latter is greater than the height of the passage. With such a refinement, it is achieved that the supports can be moved into and out of the force transmitting gap between the dock frame and the erection surface without the use of external auxiliary means. When placed out of frictional engagement they can be easily moved.
In another aspect of the invention, at least one of the supports which are movable on the floor is provided with a stairway. With this refinement of the invention, it is achieved that the displaceable supports at the same time create additional access ways to the working floors of the dock unit, providing shorter paths from the floor of the maintenance hangar to the outer skin of a docked aircraft.
In one aspect of the invention, at least one of the supports which are movable across the floor takes the form of a lattice strut structure. This refinement of the invention is advantageous with regard to a good load-bearing capacity of a movable support combined with low weight, and with regard to accommodating a relatively large stairway which is easy to climb.
In another aspect of the invention, at least one of the displaceable supports is pivoted. This refinement of the invention is advantageous because the guidance for the movement of the displaceable support between the prop position and the clearance position can be realized at low cost.
In one embodiment, the pivot axis of at least one of the pivoted supports is disposed horizontally and transversely with respect to the longitudinal direction of the frame. This variant has the advantage that the pivoted support is located within the same transverse or lateral spatial area both in the prop position and in the clearance position.
In another aspect of the invention, at least one of the supports includes a hydraulic cylinder or a threaded spindle. Such a refinement of the invention according permits simple adjustment of the length of the adjustable supports, whether in order directly to create a passage for the aircraft wing or in order to remove the support from frictional engagement between the dock frame and the erection surface in order to ensure easy movability.
In yet another embodiment, the dock unit includes at least one further, inner support which is displaceable between a prop position supporting the frame and a clearance position unblocking the space between the frame and the floor. Such a dock unit makes use both of the possibility of further inner displaceable supports and of the possibility of suspending the dock frame. In this way, the forces which must be absorbed by other elements can be spread when the outer support or other supports are moved to the clearance position.
In one embodiment of the invention, the suspension arrangement includes a crane. If a crane is used in the suspension arrangement, the force exerted on the frame of the dock unit can be easily adjusted and the suspension arrangement can be realized by a means which as a rule is already provided in any case for other tasks in the maintenance hangar.
In one such embodiment, the crane is carried by a crane trolley which runs on a crane rail fixed to a roof structure. For example, a ceiling crane which for the remaining time is provided for moving heavy loads in the maintenance hangar can be temporarily used for docking and undocking.
Alternatively, an embodiment may include a crane which is carried by a vehicle. In particular, a drivable crane which likewise is present in most maintenance hangars can be used.
In another embodiment, presence sensors may be arranged in front of and/or behind the displaceable supports to respond to the presence of an object in the space located between the frame and the floor. In particular, it is automatically monitored whether an obstacle (in particular a section of an aircraft) is located in the environment of the path through which the displaceable support passes. The output signals can be used in controlling the drives which act on the displaceable supports.
In a preferred embodiment, position indicators which indicate whether the movable supports are in their prop position or in their clearance position. In such an embodiment, the momentary positions of the displaceable supports can be monitored. The output signals of the position indicators co-operating with the supports can be used to activate displays and alarms or can directly influence the motion of the aircraft during docking or undocking.
In another aspect of the invention, a control circuit for a drive and/or for a brake which co-operate in a driving/braking manner with the aircraft, which control circuit activates the drive and/or releases the brake in the presence of an output signal of a presence sensor only if an output signal for the clearance position associated with the clearance position of the displaceable inner support which is next reached is deceived at the same time from the position indicator associated with this support. Such a structure ensures that an aircraft can be moved into or out of the dock unit only to the extent that a passage accommodating the wing of the aircraft has already been created by moving supports from the prop position to the clearance position.
In yet another aspect of the invention, the frame is movable in a transverse horizontal direction with respect to the longitudinal direction of the frame. This measure is advantageous because it allows the movable supports to be provided closer together, since the width of a wing generally decreases markedly towards the free end. This measure also simplifies the maneuvering of the aircraft in and out between the dock units.